JPH03501603A - Ultra-high purity halide and its manufacturing method - Google Patents

Abstract

(57) [Summary] This bulletin contains application data before electronic filing, so abstract data is not recorded.

Description

[Detailed description of the invention] Declaration of halogen' and its U-law le 匪 ■ 1 ken The present invention can be used for glass products such as optical fibers, solid noses, and dielectric materials. The amount of salt contained in the halides is only a few ppb or less. Extremely pure halides and their production methods that are not allowed even in Regarding.

Zirconium, hafnium, and aluminum by chloride, bromide, and iodide This salt (hereinafter referred to as "precursor salt") is capable of reacting with a fluorinating agent and has ultra-high purity. This produces a certain amount of fluoride (hereinafter referred to as "formed salt"). However, impure cations and The content of impure oxides is extremely small, and the amount of transmitted infrared loss is small High-quality fluorinated glass, useful for applications where The production of ZBLAN) J requires mass production of ultra-high purity fluoride. is required. The present invention particularly provides a method for purifying precursor salts that yields product salts in such amounts. Regarding.

Metal fluorides for the production of infrared-transmissive glass are used in the infrared region with wavelengths ranging from 2 to 4 microns. To minimize absorption due to the spectrum, e.g. transition elements, rare earth , and the content of impurities must be very small with respect to hydroxide ions. do not have.

Also particulate materials like metal oxides, carbides, carbon, coke, phosphides etc. act as scattering centers for electromagnetic radiation, resulting in undesirable attenuation. Therefore, it is an essential requirement that they must not be present.

Such impurities are typically free from purified fluorine compounds used in glass manufacturing. Although it seems to be related at first glance, the minute amount that the present invention is concerned with is by the use of particulate materials within the can also be easily mixed in.

In that sense, this invention deals with cationic substances that must be made non-volatile or removed, gold The complexes and compounds of the genus are extremely diverse.

The problems raised by the presence of such substances are discussed, for example, in the ``4th Halogenated Gas Proceedings of the International Symposium on Russ e 4th InternationalSymposium on Hali deGlasses) J (1987).

The stringent purity requirements for such glasses are such that, for example, the desired salt The concentration of a substance is only a few pI)b or lower, and conventionally The available technical limits were often exceeded. Commercially available fluoride is Even if the material is said to be of very high purity, the concentration of impurities is 10 to 1. ,000ppm.

Therefore, the improvement rate is, for example, 1.000 to 1,000 compared to what is currently available. There is a need to significantly improve the purity by a factor of 0,000. Ru.

Known purification methods for producing zirconium fluoride and hafnium fluoride include , recrystallization method for electromotive side displacement (ESD) reinforcing distillate of ZrFa, solvent extraction method, and dehydration process (the subject of U.S. Pat. No. 4,578°252), and Chemical vapor purification process (CVP) of zirconium: U.S. Pat. No. 4,652,438 subject of the specification).

The recrystallization method and the solvent extraction method are methods of finishing the purification at the Zr0C1* stage. However, in the step leading to ZrF a, a considerable amount of impurity, for example 2 to 10 times as much, is added. Things are taken in.

Furthermore, these methods leave oxide and hydroxide impurities in ZrF. The fact that there is a tendency is also an undesirable point.

The purification ability of the anhydrous method basically reduces impurities, such as metal chlorides. Based on the excellent reducing power of solid reducing agents or electrodes that reduce the volatility of However, there are limitations to its practical application due to the limitations on mass transportation.

For example, in the CVP method, the calculated concentration of iron in the produced ZrF4 is approximately 0. 007 ppb, i.e. F19CI in contact with metallic zirconium at 923° However, as shown in Table 2 below, the achieved concentration is actually It is about 2009 pb, and there is a discrepancy of 4 orders of magnitude.

The same applies to the known distillation purification of ZrF a from BaF++-ZrF4 solution. There is a shortage of Distillation without ESC reinforcement results in unacceptable concentrations of iron. Products containing impurities are manufactured. Even if the ESC is reinforced with improved methods, The theoretical thermodynamic limit is far short.

Also, repeated distillation does not seem to provide any improvement.

These data indicate that due to the limitations of large-scale transportation, approximately 10 to 100 It is not possible to achieve or approach the desired impurity concentration of ppb. It means that there is.

It is therefore an object of the present invention to produce selected metals of previously unattainable purity. A method for producing a fluoride generating salt and its precursor salt, the method comprising: inputting energy; Provides a method with very low consumption of chemical components and the need for complex equipment There is a particular thing.

It is also an economical and relatively simple process that is relatively easy to control during operation. temperature, volatilization rate, removal of precursor salts, and subsequent formation of product salts. can be easily performed in batch, semi-batch, or continuous operations. and in relatively large quantities, for example, batches that were previously possible using the above-mentioned known process. of precursor salts, and their fluorinated salts, efficiently and effectively. It is also an object of the invention to provide a method by which it is possible to manufacture.

These and other objectives are achieved by the method of the present invention.

Broadly defined, the method involves the use of impurity-containing zirconium, hafnium Alternatively, a method for purifying aluminum chloride, bromide, or iodide precursor salt, comprising: or more types of alkali metal or alkaline earth metal halides; forming a thermal melt with the precursor salt; The vaporization temperature is maintained at 60°C, and the liquid is liquid at the vaporization temperature and is inside the thermal melt. While placing the hot melt in a reduced state using a reducing agent that is movable at evaporating the precursor salt from the hot melt; and adding the evaporated pure precursor salt to the hot melt. This is a purification method consisting of the steps of isolating from.

Brief description of the drawing FIG. 1 is a schematic diagram outlining a typical apparatus useful in practicing the present invention.

Figure 1a is a typical sealed structure.

FIG. 1b is an enlarged partial sketch of the nozzle of the reactor shown in FIG. 1. FIG.

Day-! Day The entire mechanism and device used in the present invention will be explained as follows: 1. Kiln furnace (12) A molten salt solution (10) is stored in a sealed container (15) lined with glass or quartz. It is tolerated.

Piping (11) for transporting hydrogen or inert gas is a sealed container (15) and connects it to a gas supply (not shown).

The pipe (11) extends below the surface of the molten salt or eutectic mixture.

The second structure (13) surrounding the thermocouple (14) is also inside the sealed container (15). It reaches below the surface of the melt (1O) and senses the temperature of the melt. The detected temperature is transmitted and displayed to the operator (not shown). Zoom in on a typical sealed structure and show.

Piping (16) transports the ZrCl4 vapor onto the melt (10) in the sealed container (15). from the space to a second container (20), where this chloride vapor is transferred to ZrF4 and contact with HF under conditions that produce HCI.

Other details, such as temperature, are particularly important for the operation of the entire reaction system. I will explain it in.

In the process of the present invention, the halogenated precursor salt is volatilized, while impurities cations, such as FeCl, keep the melt or liquid in reducing conditions. This makes it non-volatile.

Such halogenated impurities and others are thereby reduced and made more non-volatile. It is kept in a state of onset.

As explained in more detail below, in contrast to traditional methods, the connection of hot melt components The catalytic surfaces, precursor salts, and reducing agents are sufficiently mobile that impurity accumulation is comparatively Not very accurate. As used herein, the term "mobile" refers to substances that are highly diffusible. This means that it is possible to

Therefore, the extremely difficult transportation associated with the conventional dehydration method described above The problem is virtually completely avoided by this process.

Furthermore, the evaporation of ultrapure precursor salts inevitably involves a heat transfer interface between the liquid phase and the same phase. , the production rate can be easily controlled compared to conventional processes.

The amount of reducing agent used is such that all impure cations are stoichiometrically reduced. Depending on the reaction system and the need for desired efficiency, The amount can be less than or significantly in excess.

We present a model for calculating the content of impurities in products vaporized from molten salt solutions. Show.

The ideality of the vapor phase (pressure according to the ideal gas law = fugacity) and the theory of solutions Assuming a degree of imagination (according to Raoult's law).

That is, the following equation %formula% (where P+ is the partial pressure of component i above the solution, and Xl is the molar fraction of i in the solution. , Po, respectively represent the vapor pressure of pure i at a specific temperature) holds true. .

Impurities shall not interact with each other, and regarding the amount of impurities, XI41 = O. It is assumed that only a small amount exists.

Considering that the vapor is removed and concentrated, p+/P-1e+4( = 1 atm) represents the concentration of i in the product ZrC1a.

As the distillation continues and the product is removed, the impurity concentration in the melt increases, and the concentration in the product increases. will also rise.

If left as is, the product would be unacceptable.

Serial publications [American Institute of Chemical Engineers Modular Education Series (AIChE Mo MacDuffie (N, The paper “Batch Distillation” by GM McDuffie ion) J [Module No. 81.5, American Institute of Chemical Engineers (AIChE) 19 As described in [Published in 1980], this phenomenon occurs in the case of one-stage (no reflux) batch distillation. Rayleigh's formula %formula%) (In the formula, S is the number of moles remaining in the molten salt solution, and F is the number of moles in the original charging material. , α is the fraction of vapor pressure, i.e. Par. , 4 (=1 atm)/P, where Xs is melting Xf is the mole fraction of ZrCl4 in the salt solution, and Xf is the mole fraction of ZrCl4 in the feed material. (respectively) can be calculated.

Using the above formula with storage conditions such that number of moles of distillate D = F-8, At any point in the distillation, the salt solution and the (totally mixed) average The concentration of impurities in the produced ZrF a can be calculated.

This interrupts the distillation to prevent impurities in the product from reaching unacceptable concentrations. It is equivalent to knowing the point in time when something must be done. Furthermore, conversion to ZrF4 without recovery 0.1.10.50, and impurities for distillation up to 99% is calculated as follows.

A detailed study of the vapor above the condensed phase of chloride containing impurities reveals that to some extent The presence of a degree of polymerization is usually evident.

For example, FeC12, NiC1*, and CoC1* have at least some It is known that CuC1 contains a dimer, and CuC1 is vaporized as a trimer.

At a given vapor pressure, the monomer is transported twice, three times, etc., but the Xi in the equation of Hall's law becomes 1/2, l/3, etc.

Therefore, the agglomeration state of the molecules in the vapor phase is can be ignored.

However, it is possible that the solution and vapor phases have different degrees of complexity, and this It appears as a deviation from Raoult's law.

However, a very strong effect such as a deviation in the direction of increase of 100 times, for example, This is likely to affect the validity of the data presented here.

Table 1 shows the results of calculating the amount of impurities in the product.

(Margin below) Double precision is required for calculations, and statistical software called ASSIST (ASYST: registered product name) is used. Calculations were performed using a software package.

Vapor pressure data is calculated assuming a temperature of 400°C (maximum operating temperature for salt solutions) This is what I did.

For transition elements, these data are from Reference (a) (for TE) listed below. In addition, rare earth elements were taken from Reference (b) (for RE) listed below.

If there was any ambiguity in the vapor pressure equation, the higher value was used. on solution The vapor pressure of ZrC11 on the other hand is always 1 atm.

The impurity concentrations described herein are determined by Northern Analytical (N Sublimated ZrC obtained from Aanlytical Inc.) 1a sample, converted to mole fraction and then, where appropriate, used for values less than or equal to .

(a) Colton (R, Colton) and Canterford (J, H.

Canterford): r Halide of the first row transition element s of the First Row Transition Metals ) J, London, Wiley Interscience, 1969.

(b) Brown (D): r-lanthanide and actinide Halides of the Lanthanides dActinedes) J, London, Wiley Interscience Ltd. 1 Published in 968.

The concentration of impurities in the released product is very low even at high yields. Sometimes.

This is due to the concentration of impurities in the molten salt due to its low initial concentration and low volatility. This means that even shrinkage is not a problem.

Such purity is achieved by Folweiler (R, C, Folweiler) and Pin “The 4th International Conference on Halogenated Glass” by F. Recorded in the Proceedings of the Symposium (held in Monterey, California in 1987). This exceeds the requirement of 1 dB of attenuation per 1 km for 30 times. .

Thermal melts commonly used at present include, for example, alkali metals or alkaline earths. Produced by simple melting of anhydrous halides of one or more metals has been done.

Particularly preferred halides are sodium or potassium chloride. The reason for this is that they are inexpensive, easily available, and desired. The 1-atm pressure isobar of the precursor salt vapor pressure is advantageously easily obtained at low temperatures. This is because it easily satisfies the requirements for a melt.

This is preferred because the purified precursor salt vapor easily resists the ambient pressure. When vaporized and delivered, it combines with fluorinating agents to form fluorogenic salts. be.

Another requirement that is met by using these halides is that these It is essential that the salt be non-volatile at the process temperature and that must not be transferred to

Removal of impurities, i.e. contact of this melt with hydrogen gas, must first take place. This facilitates the reduction of many impurities.

The reducing agent removes salts containing impurities through the liquid phase interface due to its huge surface area. contact with a hot melt consisting of

This interface is a gas equivalent to when bubbles of a gaseous reducing agent, e.g. hydrogen, are passed through the melt. It may be a phase-liquid phase interface, or an electrically positive metal with a low melting point, For example, sodium, potassium, magnesium, calcium, lead or zinc, and their alloys are filled in liquid, sprinkled, or diffused. It may be a liquid phase-liquid phase interface.

When a liquid phase-liquid phase interface is used, the reducing agent substrate can be continuously renewed; As a result, accumulation of impurities therein can be avoided.

In contrast, the gas phase-liquid phase interface as in the CVP method, or the The liquid-liquid interface is controlled by the accumulation of impurities that occur most prominently at the reduction site. Receive a promise.

If hydrogen is selected as the reducing agent, bubble bubbles into the solution from an external gas supply. In addition, suitable metal halides such as zirconium, hafni halides of aluminum or their alloys with other metals are placed in a salt solution and the These thermal decompositions at liquid temperature liberate hydrogen from the solution while controlling the process. You can also do it.

Alloys of lead and zinc with other metals can also be used.

For example, when about 2% by weight of magnesium is melted with lead, the magnesium The low melting point alloy that aluminum forms with lead melts in salt solutions and It can be a reducing agent with reducing power.

In addition to lead and zinc mentioned above, lithium, sodium, potassium, or Highly electropositive metals, such as the alloys of E. et al., also melt at salt solution temperatures.

In addition to the direct action of metals on impure atomic species in solution, magnesium It also appears that the mechanism of action related to the immune system works.

Also, materials that do not melt at salt solution temperatures, such as magnesium, calcium, and Other metals such as aluminum can also be used.

As mentioned above, these interact with the solution to keep the reducing agent mobile.

Without regard to any particular theory, these highly electrically positive metals are Reduces a portion of the salt salt to a less valent state, making it somewhat soluble in solution and This is thought to form a precursor salt of atomic species with strong reducing power against impure cations. Ru.

□For example, a small amount of magnesium metal added to a solution will cause a certain amount of zirconium tetrachloride to Reacts with zirconium and requires zirconium in an oxidation state such as divalent or trivalent. Magnesium itself is soluble in solution, forming reduced atomic species that Efficiently converted to gCl2.

Low valence atomic species of zirconium are impurity atoms such as divalent or trivalent iron. Powerfully reduces seeds to non-volatile forms.

When experimenting with magnesium, the salt solution initially appears pale yellow or gray. However, as the magnesium dissolves, it develops an intense purple color. Ru.

Thus, although magnesium does not melt at salt solution temperatures, the present invention nevertheless This results in a mobile reducing state that is suitable for implementation.

Aluminum is a precursor salt that reaches a low valence state under salt solution conditions. Even in cases where this appears to be the case, highly electropositive metals in salt solutions The action of producing metals in the elemental state changes the form of the precursor salt into a fine powder with a large surface area. and keep it very diffused within the solution.

In this case, stirring the solution will aid its diffusion.

This form is different from the metal block form used in conventional technology. It is also much more convenient.

In all cases where the reducing agent is strong enough to reduce the precursor salt , a slight loss in yield is inevitable due to the non-volatile nature of the reduced atomic species. do not have. However, this is not the case unless the starting material is very contaminated. In all cases it is easily possible to limit it to a few percent.

The precursor salts of the present invention are all solids that sublimate and typically form liquids only under pressure. to be accomplished.

However, the hot melt or hot melt of the present invention works as a "chemical control substance". The vapor pressure of the purified salt is controlled within a range convenient for processing, and liquid-solid heat transfer is achieved. bring benefits to the system.

In this regard, we discuss the use of fluorinating agents to convert purified salts into ultra-pure fluoride. The flow is adapted to take up the volatilized salt to ensure optimal utilization of the fluorinating agent. It can be easily adjusted to suit your needs.

If the precursor salt and hot melt material do not form a eutectic system, keep the interior homogeneous. By moderately stirring the melt with the intention of sublimating the precursor salt or enables control of vaporization and enables effective purification according to the present invention. This should be noted.

Another advantage to the release of purified precursor salts from hot melts or solutions is that hot melt Any body halides carried into or produced in solution It also "wets" the particulate material.

Therefore, any oxides, coke, etc. that may be present in the precursor salt are advantageously removed from solution. kept inside.

Zirconium, hafnium, and aluminum oxides are very stable; Oxides are formed from any oxygen or moisture that can enter the reaction system. These impurities collect at the bottom of the solution as a sludge rich in It will be removed.

Regarding the use of molten salts to purify halide vapors, see e.g. Transactions of the Metallurgical Section of the Society of Mineral, Metallurgical and Petroleum Engineers fMetallurgfcal 5ocfety of AIME) No. 224゜ No. 965 (1962). This operation uses steam as bubbles to dissolve the salt. It is a type of cleaning method that involves passing it through a liquid.

The present invention does not require transportation and purification treatment of impure vapors, but rather It is produced directly from a hot melt or from a hot melt.

Therefore, the purification and manufacturing steps are separated, so that the purification reaction is controlled by the flow rate, Since it does not depend on bubble size, blowing efficiency, etc., it takes enough time. You can make it happen.

Based on the thermodynamic calculations detailed below, the process according to the conventional technology and the present invention The data regarding the purification compared to that of

Based on this data and the above-mentioned material transport problems of the conventional dehydration process, the present invention From the viewpoint of physical comparison with the process of Although solid pieces have large dimensions, the surface area for electron transfer in redox reactions is quite small. Sai. .

In such solid reducing agents, there is little or no mobility and Therefore, there is no renewal of the reducing substrate, whereas the mobile liquid reducing agent of the present invention It is the New things are happening all the time.

Table 2 Impurity for ZrF4 (ppb) "Impurity 0.01dB/km NRL" From BaF2 cvp method 5 ZrC1, ZrF4 recrystallized to achieve emptying Required value of the present invention at the beginning 2 Method “ESC distillation 4 Representative method Fe O, 3 5005002000,001Co　O,3<300　nd’,<10　4xl O-'Ni 3.0 <70 <20 2xlO-'Cu 10,100 <4 0nd, <10 0.04Ce <200 <10-' Pr<200<10'-' Nd　O,5<800　<10-' 1: For uniformity, convert to wood table units when appropriate.

22 “Proceedings of the 4th International Symposium on Halogenated Glasses J (1987 The discussion of Lu (G, Lu) and Aggarwal (1, Aggarwal) published in From the sentence.

”: held in Washington, D.C. on December 12, 1986 r　NRL High Purity Fluoride Pre-announcement conference 71/ns (NRL High Purity Fluo rides Pre-proposal Conference) J From the presentation by Shah (C, F, Fisher).

4: Materials Science Forum e Forum), Volume 5 (1985), pages 19-34, Robinson ( From a paper by M. Robinson.

5: Materials Science Forum, Volume 5 (1985) 43-48 Folweiler (R, C, Folweiler) and Günther on the page From the paper by (D, E, Guenther).

8 = No data.

Specifically describing the process of the prior art, metal zirco is chlorinated to become ZrCl4. The CVP method has transportation constraints in that the surface of Ni becomes iron-rich. be.

Therefore, iron is chlorinated faster than it can diffuse into the interior.

Therefore, the discrepancy between the chlorination rate and the diffusion rate causes The mechanism of action of impurity retention, which is the reduction condition set by the presence of Instead, the concentration of iron in the product is much higher than expected.

Distillation of BaF2-ZrF4 is in a more favorable position and actually reduces the amount of iron in the product. The concentration is a number calculated based on F e F and the relative vapor pressure of ZrF4. very close to the value.

Regarding the option of reinforcing with ESC, again, increased contamination of the reducing agent surface Transport of iron into the liquid and then into the product vapor occurs.

This also means that the vapor pressure of fluoride is closer to that of impurities than chloride. In this respect, it is clear that this is a disadvantage for purifying fluoride.

Also, regarding the vaporization of ZrF4, which contains a large amount of impurity oxides in the reaction system, , a heat insulating surface layer is formed and thickened on the surface of the hot melt, and the vaporization rate of ZrF4 increases. It works to lower the

The above findings for prior art processes indicate that these methods have The disadvantage is that the interval width is determined by the desired time interval for material production. highlight things.

There is no theoretical reason for the speed of these processes to be comparable; the reality is Certainly far from it.

For the CVP method, the experimental equipment essentially controls the rate of chloride addition; The scale is such that chloride can be produced at a convenient rate.

However, this chlorination rate is the refining rate, which is the diffusion rate of iron into metallic zirconium. is not suitable at all.

A particularly preferred embodiment of the invention involves the purification of anhydrous zirconium tetrachloride. child If the hot melt or hot melt has a molar ratio of sodium chloride to potassium chloride It is composed of a mixture of about 8=29, and the reducing agent is metallic lead.

In this example, ZrCL is melted together with the NaCl-KCl mixture and Forms a mobile liquid at approximately 230°C.

Journal of Chemical Engineering Data, Volume 19 (1974) Kim (J, D, Kim) and Spink (D, R, 5) published on page 36 According to the phase diagram described in the paper by Pink), when heated at 1 atm, 68 mol% of ZrCl4 and a mixture of 32 mol% NaCl and KCI in a molar ratio of 8:29. The mixture generates ZrCL vapor at approximately 330°C.

With continued heating, the composition of the solution changes to a point where ZrC1a is depleted along the 1 atm isobar. The point at which the solid phase of (Na,K)2ZrC16 appears, that is, approximately It reaches 400°C.

After that, the solution is no longer homogeneous and the temperature must rise rapidly to maintain 1 atm. degree is required.

Preferably, the solution is cooled and refilled at this point. In this example, the molten metal Lead was added to the solution container at a concentration of approximately 0.1 mol per 1 mol of ZrCL. Ru.

Lead does not react with either solution materials or precursor salts, but it does react with impurities. , for example, to reduce impure cations.

By circulating between the two temperatures mentioned above, the initial concentration of acid in the solution is reduced to 10k. g, approximately 3.3 kg of purified ZrC11 is formed before recharging is required. .

In hot melts, several types of impurity metal ion sequestration mechanisms operate simultaneously. First, the solution The operating temperature is low and the volatility of impure chlorides is consequently low. Second, liquid reduction agents, such as hydrogen or lead, can destroy, for example, nickel, cobalt, and copper cations. Chemically reduced to non-volatile metals.

In the case of copper, it is not only reduced but also extracted and sequestered in the lead matrix. It becomes.

These reducing effects do not interfere with the purification of the lead substrate, but it is important that this This is because it is basically constantly updated.

Third, the solution is such that stable binary compounds are formed from solution components and impure chlorides. give an opportunity.

Examples of such known compounds include Na, FeCl4, KFeCls, K2 Examples include CoC14 and KjNdC16, but these do not form a complex. It has a lower vapor pressure than the solution component.

The net effect of all these factors is to bias the production of purer ZrCl4. That is.

As ZrCl4 is released from the molten salt solution, impurities are formed and gradually Appears in products with increasing frequency.

However, because the difference in vapor pressure between ZrCl4 and impurities is very large, recovery is not possible. Approximately 80% of the available ZrCL can be extracted before the concentration of impurities in the product doubles. is possible.

The expected concentration of impurity in the product per initial ppm of impurity in the hot melt is 1 Using the equation for the Rayleigh distillation of stages, α, i.e. ZrCl4 and impure salts The relative volatility of the chloride is used as the ratio of the vapor pressure of the impure chloride to 1 atm. It is therefore calculated as a function of removal from solution.

At 400°C for FeC1z, CoC1*, NiC1g, and CuC1 The vapor pressure data for This is an excerpt from ``Metal Halides.''

In this calculation, the reducing conditions in the solution reduce iron and copper to FeCl2 and C, respectively. It is assumed that there is no effect on purity other than keeping it as uC1.

Therefore, this is a conservative estimate of purity.

(Margin below) Impurities At 400℃, vapor pressure of hot melt or hot melt by percentage of yield in melt ppb of impurity in the product relative to the initial impurity of 1 ppm (torr) O% 1015 FeC1z 2.5xlO-' 0.0004 0.0005 0.0006C uC11,3xlO-' 0.24 0.25 0.4NiC129,2xlO -'2xlO-'2xlO-'4xlCl''6CoC1t 1.1xlO -'2xlO-'4xlO-118xlO-'Looking at this, only copper is I) I) Close to the order of b. This data corresponds to FeC1* and FeC1* for iron and copper, respectively. No reducing agent is used at all, which is stronger than hydrogen, which has sufficient ability to maintain CuC1. This is for special cases.

In the above example, the raw material precursor salt may contain several thousand ppm of impurities. This shows that using the method of the present invention, it can be further purified to a concentration of ppb or less. are doing.

Therefore, raw materials that are otherwise unsuitable for use can be readily used with the present invention. Becomes Noh.

Based on the above, the reducing agent selected includes several substances belonging to light and heavy classes. It turns out that it is possible.

For example, metal halides that can be used include zirconium, hafni liberates and decomposes hydrogen gas within the operating temperature range of a single sample or a salt solution. Compounds with other metals can be included.

Similarly, low melting point, i.e., electropositive Metals such as lithium, sodium, and potassium, or their alloys Although it does not melt at the salt solution temperature, as shown in the following equation, the precursor halogen A lower halide that reacts with a compound and has good diffusion and strongly reduces impurities. Electropositive magnesium, calcium, and salts of reducing agents soluble in solution , and metals such as barium can also be used.

Mg + Zr” (dissolved in solution) = Zr24 (dissolved in solution) + Mg” (dissolved in solution) ZrQ (dissolved in solution) + Fe'' (dissolved in solution) - + Fe + Zr' (dissolved in solution) Preferred practices of the invention preserve the mobility and diffusivity of the reducing agent, as described above. It will be done.

What has been detailed above is also applicable to HfCl4, with slight changes in the parameters, For example, only a few degrees Celsius change in operating temperature is required.

In the case of aluminum, similar physicochemical properties are found in the AlCl3-rich molten salt aluminium. It is also applicable to mixtures with alkali metals.

The eutectic temperature in such a reaction system is lower than that in the corresponding ZrCl4 reaction system. The volatility of the impurities is much more favorable since the temperature is about 100°C lower.

The above concept can be extended to bromide and iodide reaction systems without extra experimentation. can be stretched.

The final step in the process is a halogen exchange reaction of the purified precursor salt with a gaseous fluorinating agent.

The chemical stability of fluorides is so great that, for example, with respect to precursor halides, For example, the reaction equilibrium with anhydrous hydrogen fluoride can be reached even if there is only a slight excess of fluorinating agent in the gas stream. However, the trend is overwhelmingly towards fluoride formation. At this stage, the ZrCl4 vapor is , into a reaction chamber maintained at approximately 400° C. and contacted with a stream of gaseous HF.

This reaction chamber contains equipment for recovering solid fluoride products and exhausting by-product MCI gas. It may be in the form of a condensation vessel, for example, with a vent for exiting.

Production of high purity glass by maintaining certain zones of the reaction chamber at 350°C All unreacted purified salts that are inconvenient to the product are discharged with HCI and incorporated into the product. It will become less common.

This method also has very significant advantages, including lower overall operating temperatures. That's true.

Therefore, we choose common construction materials that suppress the introduction of impurities into the reaction system. It becomes possible to use it.

Such materials include, for example, zirconium metal and magnesium metal. Ru. They form a protective fluoride coating at low temperatures, but at higher temperatures will react.

Such materials can be placed in high-purity products and have many Minor corrosion poses no threat to product purity. In the conventional technology Higher temperature methods, such as platinum or glassy carbon, We have no choice but to use it.

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Claims (20)

[Claims] 1. Zirconium, hafnium, or aluminum chloride, bromide, or iodine 1. A method of purifying a chemical precursor salt comprising: one or more alkali metals; Alternatively, a thermal melt of the alkaline earth metal and the precursor salt containing impurities is formed. the stage of While applying reducing conditions to the hot melt using a reducing agent, the hot melt is reduced to about 3 Maintaining a vaporization temperature of 30 to about 460°C to vaporize the hot melt from its impurities. and isolating the volatilized purified precursor salt from the hot melt. A method for purifying the precursor salt, characterized in that: 2. The precursor salt refinement according to claim 1, wherein the temperature of the hot melt is maintained at about 300 to about 450°C. Manufacturing method. 3. one or more hydrogen, methane, atom, etc. all diffused in a hot melt; ammonia, molten zinc or molten lead with lithium, sodium, potassium or These alloys, magnesium, calcium, barium and their alloys, using metal hydrides of ruconium or hafnium and mixtures thereof. 2. The method for purifying a precursor salt according to claim 1, wherein reducing conditions are maintained by: 4. The halide in the hot melt, the molar ratio of NaCl/KCl is about 1:10 to about 1: 1. Preparation of the precursor salt according to claim 1, which is a mixture of sodium chloride and potassium chloride. Manufacturing method. 5. 5. The method for purifying a precursor salt according to claim 4, wherein the molar ratio is from about 1:5 to about 1:3. 6. 5. The method for purifying a precursor salt according to claim 4, wherein the molar ratio is about 8:29. 7. A method for purifying a precursor salt according to claim 1, wherein the hot melt is maintained under a pressure of about 1 atmosphere. . 8. The precursor salt was ZrCl4, and the reduction conditions were such that the molar ratio of ZrCl4/Pb was The precursor of claim 1 maintained by about 20:1 to about 5:1 molten lead. Method for refining salt. 9. The initial molar ratio of precursor salt to halogenated hot melt is from about 9:1 to about 5:1. The method for purifying a precursor salt according to claim 1. 10. The precursor salt is ZrCl4 or HfCl4, and at least 8 The temperature of the hot melt is increased from about 330 to about The method for purifying a precursor salt according to claim 9, wherein the precursor salt is maintained at 400°C. 11. Claim 1, wherein the process is carried out in a container made of metallic zirconium or metallic magnesium. A method for purifying precursor salts of. 12. The volatilized and isolated precursor salt is contacted with a fluorinating agent and converted to fluoride. The method for purifying a precursor salt according to any one of claims 1 to 11. 13. Fluorinating agents such as HF, NF8, F2, SF4 or SF6, AsF5, and 13. The precursor salt according to claim 12, wherein the precursor salt is one or more of rare gas fluorides. Purification method. 14. The precursor salt is zirconium or hafnium chloride, and halogenated hot melt is used. The melt is a mixture of sodium chloride and potassium chloride, and the reducing agent is lead. A method for purifying a precursor salt according to claim 1. 15. A highly purified precursor salt prepared by the method according to claim 1. 16. High purity fluoride prepared by the method according to claim 12 or 13. 17. The reducing agent is at least one of metallic lead or metallic zinc diffused into the hot melt. hydrogen, methane, or ammonia purged into the hot melt. 5. The method for purifying a precursor salt according to claim 4, wherein the precursor salt is at least one of the following. 18. Impure ZrCl4 and reducing agent are continuously charged to the hot melt and Claim 1, wherein the purified ZrCl4 vapor is continuously removed from above. Method for purifying the described precursor salt. 19. Zirconium, hafnium or is a purified fluoride of aluminum, and the concentration of impurity cations in it is A pure fluoride characterized by the following numerical value per billion parts of the fluoride: . Fe...<about 10-3 Co...<about 10-4 Ni...<about 10-4 Cu...<about 10-1 Ce...<about 10-6 Pr...<about 10-6 Nd...<about 10-6 20. The precursor salt, which is first charged into the hot melt, is purified by standardization and ZrCl4 or Hf where the concentration of thione is less than about 100 ppm relative to the precursor salt The method for purifying a precursor salt according to claim 1, wherein the precursor salt is purified as Cl4.